The short version
Both wrap a real link behind an ad wall, and both are fully skippable. The difference is weight: ouo.io is a lighter, standard wall, while exe.io is a heavier, premium one with an extra verification step.
That single difference explains almost everything below, from how long each takes to resolve to whether you meet a captcha.
ouo.io: a standard ad wall
ouo.io uses a fairly typical flow: a countdown, a 'get link' button and a page or two of ads. It is a standard-tier shortener, which means resolving it is quick and reliable.
In practice an ouo.io link resolves in just a few seconds. You skip the timer and the ad pages and land on the real destination almost immediately.
exe.io: a heavier, premium wall
exe.io (and its siblings cuty.io and exeygo.com) layers on a tougher challenge, including a verification step before the link is released. We treat it as a premium-tier wall.
That extra protection takes longer to clear, so an exe.io resolve can run up to about a minute. The live progress on screen shows you it is working through the steps.
The captcha difference
This is the clearest split between the two. ouo.io normally gets you through with just a countdown, while exe.io adds a 'confirm you are human' style check on top.
With Link Skipper you never touch either one: whichever wall a link uses, you get the real destination back without a timer to wait out or a box to tick.
Which is faster to skip
If speed is all you care about, ouo.io resolves faster because its wall is lighter. exe.io is slower but still fully resolvable, you just wait a little longer for the protected step to clear.
Either way the outcome is the same: the real destination with no ads. Open the ouo.io or exe.io guide to skip them yourself.